Part of #Self Organizing Map and SRTM: Application in Yardangs Identification in the Lut Desert, Iran# :
Publishing year : 2009
Conference : Geomatics conference 88
Number of pages : 13
Abstract: Yardangs, an exclusive landform due to intensive wind erosion, cover a large area in the hyper-arid Lut desert of Iran. The NASA Shuttle Radar Topography Mission (SRTM) has provided Digital Elevation Models (DEMs) for over 80% of the time, using a self-organizing map (SOM) as an unsupervised algorithm for artificial neural networks for analysis and characterization of yardangs. of the land surface. Version 3.0 SRTM data provided by the CGIAR-CSI GeoPortal are the result of significant editing efforts on the SRTM DEM produced by NASA. The SRTM 3 arc seconds data were re-projected to a 90-meter UTM grid. Two-dimensional quadratic surfaces with a moving window size of 5 5 were fitted to this DEM. The first derivative, slope steepness and the second derivative, the minimum curvature, the maximum curvature, and the cross-sectional curvature were calculated as geomorphometric parameters and were used as inputs to the SOMs. 42 SOMs with different learning parameter settings, e.g. initial radius, final radius, number of iterations, and the effect of random initial weights on the mean quantization error were investigated. A SOM with a low average quantification error (0.1040) was used for further analysis. Feature space analysis, morphometric signatures, three-dimensional inspection, auxiliary data like Landsat ETM + and high-resolution satellite imagery from Quick Bird
facilitated the assignment of semantic meaning to the output classes in terms of geomorphometric features. The results are provided in a geographic information system as thematic maps of the landform entities based on the form and the slope, e.g. yardangs (ridge), corridors (valley) or planar areas. The results showed that all yardangs and the corridors between were clearly recognized and classified by this method when their width was larger than DEM resolution, but became unrecognizable, if their width is much smaller than grid resolution. The identified yardangs and corridors are aligned with NNWSSE parallel to the prevailing direction of the strong local 120 day wind and cover respectively 31% and 42% of the study area respectively. The results show that SOM is a very effective tool for analyzing geo-morphometric features such as aeolian landforms under hyper-arid environmental conditions, providing very useful information for terrain feature analysis in inaccessible regions.